Roof construction in a low-pitched roof generally consists of a roof deck, an insulation barrier above the deck, a weather resistant layer applied to the insulation layer, and optionally a layer of heat resistant material. The roof deck generally includes materials such as wood, gypsum, concrete, steel, and the like. Above the roof deck, insulation boards are typically applied to provide thermal insulation and a uniform surface to which the weather protective layer is applied. The most common insulation boards are made of polyisocyanurate, and recovery boards are typically made of woodfiber or extruded polystyrene. Polyisocyanurate may be coated with a protective facer that can be either rigid or flexible and can be fire or flame-retardant. In a reroofing operation, the roof deck can refer to the existing roof, including the existing insulation and weather resistant layer.
Insulation or recovery boards, as they are referred to in reroofing, have been employed where the existing roof is leaking. These boards are generally applied to a built-up roof deck to provide a uniform surface when recovering an existing roof. The most common recovery boards are made of woodfiber or extruded polystyrene. The woodfiber is typically coated with a thin layer of asphaltic material on one side, but extruded polystyrene typically does not contain a facer.
To seal the roof from the elements, the insulation or recovery boards are typically covered with various materials including molten asphalt, modified bitumen membrane, rubberized asphalt, or an elastomeric composition such as EPDM (ethylenepropylene diene monomer). Not all sealing materials mentioned previously are compatible with each type of insulation or recovery board. For example, molten asphalt cannot be used with extruded polystyrene. Correct combinations of sealing material and insulation or recovery board are known to those skilled in the industry.
Finally, the heat resistant layer of material, which is generally applied directly to the weather resistant layer, can include gravel, river stone, foam or a layer of mastic covered by gravel and the like.
Application of the weather protective layer can be accomplished by a number of means, usually dictated by the type of material employed. For example, sheets of a protective membrane can be rolled out over the roof and bonded together by torching or the use of an adhesive.
Although inexpensive and generally in wide use, woodfiber and polystyrene-containing insulation or recovery boards are often ineffective in hot, humid and wet environments. Particularly, woodfiber boards will disintegrate in a wet, humid environment, which is common in a reroof operation. Polystyrene will expand, bow, or distort in similar environments, especially when exposed to the extreme heat experienced upon roofs in warmer climates.
The patent literature does include panels and boards used for roofing operations. Built-up roof constructions and the components thereof, for example, are well-known in the art. With regard to insulation boards, U.S. Pat. No. 5,001,005 teaches a rigid foam board comprising a thermosetting plastic foam sandwiched between two facers; the facer comprising glass fibers, non-glass filler, and non-asphaltic binder. Likewise, U.S. Pat. No. 4,388,366 teaches a laminate insulation board comprising a plastic foam core and at least one facer sheet forming both a protective layer and a venting means for fluids; the facer sheet comprising fine glass fibers bonded together with polyvinyl acetate.
U.S. Pat. No. 5,081,810 is directed toward a building panel comprising a core sandwiched between two outer skins. The core is formed from polystyrene or polyurethane and the outer skins can include plywood or other suitable material. In lieu of plywood, the use of other materials such as gypsum has been recognized in the art.
U.S. Pat. No. 3,512,819 is directed toward modular building wall panels comprising a foamed-in-place polyurethane sandwiched between inner and outer faces of construction materials, which include hardboard, gypsum, and plywood.
U.S. Pat. No. 3,842,559 is directed toward a roof deck construction fabricated from glass-fiber-reinforced gypsum. Specifically, the roof deck includes a laminate comprising (i) a glass-fiber-reinforced gypsum board, (ii) foamed polyisocyanurate, and (iii) a layer of weather resistant plastic substance.
U.S. Pat. No. 4,037,006 is directed toward composite insulating panel-boards for use in building construction. The panel-board comprises (i) a rigid, gypsum board base panel, (ii) a self-adherent layer of foamed plastic, and (iii) water-vapor resistant, flame-retardant edge sheets covering the side edges of the plastic foam layer.
U.S. Pat. No. 4,052,831 is directed toward a panel building construction, which can be applied to a roofing system, comprising (i) a rigid board such as gypsum, and (ii) a layer of foamed plastic insulation.
U.S. Pat. No. 4,449,336 is directed toward a roofing structure comprising, from the bottom up, (i) steel joints, (ii) metal decking, (iii) a layer of fireproof material formed of plasterboard, (iv) a reservoir board such as gypsum, (v) an insulation layer, and (vi) a layer of rubber lamination.
U.S. Pat. No. 5,220,762 is directed toward fibrous mat-faced, water-resistant gypsum boards. Particularly, one embodiment teaches a roof deck system including: (i) a supporting means, (ii) a fibrous mat-faced, water resistant gypsum board overlying the means, and (iii) an exterior finishing material overlying said board. This embodiment can also include an insulating material, such as isocyanurate, sandwiched between the supporting means and gypsum board. The fibrous mat comprises glass fibers and synthetic resin fibers. When a roof deck is contemplated, the finishing material includes asphalt and roofing felt preceded by the application of a settable cementitious material over the fibrous mat-faced gypsum board.
Thus, a need still exists for a recovery board which can be exposed to moisture during installation and remain dimensionally stable while wet and during the eventual evaporation of the moisture. Use of a composite which contains isocyanurate and/or urethane foam between gypsum board and a facer that comprises a polymer, such as polypropylene, a polyamide, polymer latexes and the like, reinforced with glass strands or glass fibers and optionally a filler material, such as calcium carbonate, clay, mica and the like, makes the composite of the present invention dimensionally stable and relatively insensitive to moisture in reroofing.